Ruthenium, osmium and rhodium-2,3-bis(2′-pyridyl)quinoxaline complexes

Ru-3(CO)(12) reacts with 2,3-bis-(2'-pyridyl)quinoxaline (dpq) in benzene in the presence of either 2,2'-dipyridine (dpy) or pyridine (py) to give the mononuclear complexes Ru(CO)(3)(dpq) (1) and Ru(CO)(2)(dpq)(py) (2), respectively. On the other hand, reactions of Os-3(CO)(12) with dpq alone, or in the presence of dipyridine, yield only Os(CO)(3)(dpq) (3). Spectroscopic studies of the three complexes were consistent with the proposed structures. Reactions of RuCl3 with dpq, under reduced pressure in PhH/EtOH gave bis-[Ru(dpq)(2)Cl-2]Cl (4). Magnetic measurements showed Ru-III, d(5), to be in a low-spin electronic configuration. Three complexes, Rh-2(dpq)(2)Cl-6 (5), [Rh(dpq)(2)Cl-2]Cl (6) and Rh(dpq)(py)Cl-3 (7), were isolated from reactions of RhCl3 with dpq. The type of product was dependent on the reactants and conditions. The complexes exhibit either irreversible or quasi-reversible ligand-based reductions. In addition, the zerovalent complexes (1)-(3) displayed one metal-based oxidation in their cyclic voltammograms, due to the formation of M+ species.